JPH04360521A - Growth method of polycrystalline silicon - Google Patents

Abstract

PURPOSE:To obtain a polycrystalline silicon growth method wherein the formation of an oxide film on the interface between a semiconductor substrate and polycrystalline silicon in the conventional polycrystalline silicon growth process is prevented and contact resistance is reduced, when electric contact between the semiconductor substrate and the polycrystalline silicon is formed. CONSTITUTION:A polycrystalline silicon growth equipment is equipped with introducing pipes of HF gas and H2O gas. In polycrystalline silicon growth process, mixed gas of N2, H2O and HF is introduced after a semiconductor substrate 4 is put in a furnace core tube 2 and before the polycrystalline silicon is grown. Hence an oxide film formed when the semiconductor substrate 4 was put in the furnace core tube 2 is eliminated, and the polycrystalline silicon is grown. Thereby contact resistance is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for growing polycrystalline silicon on a semiconductor substrate.

0002

2. Description of the Related Art Conventionally, polycrystalline silicon has been grown on a semiconductor substrate by the following method. FIG. 3 is a block diagram of a low pressure CVD type polycrystalline silicon growth apparatus used in the conventional growth method.

In FIG. 3, the area around the furnace core tube 2 is a heater 3.
It is possible to arbitrarily control and maintain the temperature inside the furnace core tube. A gas introduction pipe 5 for supplying N2 gas into the furnace core tube and a vacuum pump 12 for reducing and controlling the pressure inside the furnace core tube are connected to one end of the furnace core tube (the right end in the figure). Also, the other end of the furnace core tube (left end in the illustration)
Gas introduction pipes 6 and 7 for SiH4 gas and N2 gas as polycrystalline silicon growth gases are connected to. The door 1 is used to optionally close or open the opening at one end (left end) of the furnace core tube.

Conventionally, in an apparatus having this configuration, polycrystalline silicon has been grown as described below.

That is, first, with the door 1 open, N2 gas is introduced into the furnace core tube through the gas introduction pipe 5, and the temperature inside the furnace core tube is controlled from 600.degree. C. to 700.degree. Then, the boat 11 holding the semiconductor substrate 4 is pushed into the furnace core tube from the left end opening side of the furnace core tube using a quartz rod or the like. After entering the furnace, the door 1 is closed, the supply of N2 gas is stopped, and the inside of the furnace core tube is evacuated using the vacuum pump 12 so that the pressure inside the furnace core tube becomes 0.001 Torr or less. Next, N2 is introduced into the furnace core tube from the gas introduction pipe 7.
Gas is supplied, and the pressure inside the furnace core tube is controlled at 0.1 to 0.5 Torr using a vacuum pump. After the pressure inside the furnace core tube stabilizes, increase the pressure inside the furnace core tube from 0.1 to 0.5T.
When SiH4 gas is supplied into the furnace core tube from the gas introduction pipe 6 while controlling the SiH4 gas to decompose, polycrystalline silicon is grown on the semiconductor substrate. After the growth of polycrystalline silicon for a predetermined period of time, the supply of SiH4 gas is stopped, and the inside of the furnace core tube is evacuated by a vacuum pump so that the pressure inside the furnace core tube becomes 0.001 Torr or less again. Then, a small amount of N2 gas is introduced into the furnace core tube through the gas introduction pipe 6 to return the pressure inside the furnace core tube to atmospheric pressure. Once atmospheric pressure returns, the door is opened and the boat holding the semiconductor substrate is pulled out, completing the polycrystalline silicon growth process.

[0006]

The conventional polycrystalline silicon growth method described above has a problem in that an oxide film is formed between the grown polycrystalline silicon and the semiconductor substrate.

That is, when a semiconductor substrate is placed into a high-temperature furnace core tube, since the end of the furnace core tube is open to the atmosphere,
Even if N2 gas is introduced into the furnace core tube, it is difficult to prevent atmospheric air from entering the furnace core tube. Therefore, oxygen in the atmosphere that has entered the furnace core tube causes a thermal reaction with the semiconductor substrate, and an oxide film is formed on the semiconductor substrate, and polycrystalline silicon is grown on the oxide film.

This oxide film does not pose a particular problem when the polycrystalline silicon is grown on an insulator such as an oxide film, but when polycrystalline silicon is grown on a conductor or semiconductor, etc. In other words, when electrical contact between polycrystalline silicon and the polycrystalline silicon underlayer is required, the oxide film formed at this interface makes the connection between the polycrystalline silicon and the polycrystalline silicon underlayer Contact resistance increases. In particular, due to the large scale integration of semiconductor devices in recent years, the area of this type of contact hole has become extremely small, and the increase in contact resistance due to the oxide film formed at the polycrystalline silicon interface has become impossible to ignore. .

[0009]

[Means for Solving the Problems] The method for growing polycrystalline silicon of the present invention includes introducing N2, H2O, and HF into the furnace core tube after a semiconductor substrate is placed in the furnace core tube and before growing polycrystalline silicon. A mixed gas is introduced to etch the silicon dioxide film on the semiconductor substrate.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a polycrystalline silicon growth apparatus used in the polycrystalline silicon growth method of the present invention. This apparatus has a configuration in which gas introduction pipes 8 and 9 for introducing H2O and HF gases are added to the conventional apparatus.

In the polycrystalline silicon growth apparatus having the above structure, the polycrystalline silicon growth of the present invention is carried out as follows.

First, with the door 1 open, N2 gas is introduced into the furnace core tube through the gas introduction pipe 5, and the temperature inside the furnace core tube is controlled from 600.degree. C. to 700.degree. Next, the boat 11 holding the semiconductor substrate 4 is pushed into the furnace core tube 2 from the left end opening side of the furnace core tube using a quartz rod or the like. After the semiconductor substrates are placed in the furnace, the door 1 is closed, the supply of N2 gas is stopped, and the inside of the furnace core tube is evacuated using the vacuum pump 12 so that the pressure inside the furnace core tube becomes 0.001 Torr or less. Next, N2 gas was supplied at 1 l/mi from the gas introduction pipes 7 and 9.
N,H2O gas is supplied into the furnace core tube at 200 cc/min, and the pressure inside the furnace core tube is controlled at 1 to 2 Torr by the vacuum pump 12. Next, from the gas introduction pipe 8
F gas is supplied into the furnace core tube at 10 cc/min for 1 to 5 minutes. At this time, a silicon dioxide film (S
iO2) is converted into SiF4 by the reaction of HF and H2O.
and will be removed. Note that the removal amount of the silicon dioxide film under these conditions is sufficient to be from nm to nm, and by this treatment, the oxide film formed on the semiconductor substrate when the semiconductor substrate is placed in the furnace is removed. Next, the N2, H2 O2, and HF gases that were being supplied into the furnace core tube are stopped, and the inside of the furnace core tube is evacuated so that the pressure inside the furnace core tube becomes 0.001 Torr or less. Next, N2 gas is supplied into the furnace core tube from the gas introduction pipe 7, and the pressure inside the furnace core tube is controlled to 0.1 to 0.5 Torr using a vacuum pump. Next, 20% SiH4 gas (N
2 base) at 1 l/min to grow a polycrystalline silicon film on the semiconductor substrate. The subsequent steps are performed in the same manner as in the conventional method, thereby completing the polycrystalline silicon growth step.

As explained above, in the method for growing polycrystalline silicon, the semiconductor substrate is grown by introducing a mixed gas of N2, H2O, and HF into the furnace core tube after the semiconductor substrate is placed in the furnace core tube. The oxide film formed on the surface of the semiconductor substrate when it enters the furnace is removed, and the dioxide that previously existed at the interface between the polycrystalline silicon and the polycrystalline underlying layer where contact is required is removed. It becomes possible to eliminate the silicon film, and it is possible to substantially avoid adverse effects on contact resistance.

FIG. 2 shows the relationship between contact area and contact resistance when polycrystalline silicon is grown on N-type silicon. Here, curve a is the contact resistance when polycrystalline silicon is grown using the conventional method, and curve b is the contact resistance when polycrystalline silicon is grown using the method of the present invention.

As can be seen from this figure, the contact resistance when polycrystalline silicon is grown using the method of the present invention is much smaller than the contact resistance when using the conventional method. In particular, this difference in contact resistance becomes larger as the contact area becomes smaller, and the smaller the semiconductor device is, the more effective the present invention becomes.

[0017]

[Effects of the Invention] As explained above, the present invention introduces a mixed gas of N2, H2O and HF into the furnace core tube after the semiconductor substrate is placed in the furnace core tube and before polycrystalline silicon growth. Etching the silicon dioxide film on the semiconductor substrate has the effect of reducing the contact resistance between the semiconductor substrate and polycrystalline silicon.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a polycrystalline silicon growth apparatus used in the polycrystalline silicon growth method of the present invention.

FIG. 2 is a graph showing the relationship between contact area and contact resistance when polycrystalline silicon is grown on N-type silicon using the conventional method and the method of the present invention.

FIG. 3 is a configuration diagram of a conventional polycrystalline silicon growth apparatus used for growing polycrystalline silicon.

[Explanation of symbols]

1 Door 2 Furnace core tube 3 Heater 4 Semiconductor substrate 5, 7 N2 gas introduction piping 6　　　　SiH4　Gas introduction piping 8 HF gas introduction piping 9 H2 O gas introduction piping 11 Board 12 Vacuum pump

Claims (1)

[Claims] 1. In a method of growing polycrystalline silicon on a semiconductor substrate by low pressure CVD, after the semiconductor substrate is placed in the furnace core tube and before the start of polycrystalline silicon growth, N2 is added into the furnace core tube. , H2O, and HF to etch a silicon dioxide film on a semiconductor substrate.